New Feature / Fix: Exploration mode for minimap

Implemented a new feature called "Exploration Mode" which can be enabled by the compiler Flag EXPLORE_MODE, which will force players to explore the map in order to receive a fully drawn minimap. By default, OTClient will simply draw all received tiles from the server as minimap tiles allowing players to view lower and higher floors instantly. Some people might not want this and with this patch players will have to explore all floors in order to receive a correct minimap